1. Field of the Invention
The present invention relates to structures which can be used in reactions wherein the reaction and distillation of the reaction mixture are carried on concurrently using the structures as both catalyst for the reaction and as distillation structures. More particularly the present invention relates to a rigid container having distillation surfaces thereon, the container being filled with a particulate catalyst component.
2. Related Art
A new method of carrying out catalytic reactions has been developed, wherein the components of the reaction mixture are concurrently separable by fractional distillation. Several systems have been proposed and one commercially successful uses the catalyst as the catalytic distillation structure. Such a system is variously described in U.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,250,052; 4,302,356; 4,307,254; 4,336,407; 4,439,350; 4,443,559; and 4,482,775 commonly assigned herewith.
Briefly, the commercial structure described therein comprises a cloth belt with a plurality of pockets spaced along the belt and containing particulate catalyst material. The cloth belt with catalyst filled pockets is wound into a helix about a spacing material such as knitted stainless steel wire mesh, and these "bales" loaded into a distillation column. Additionally U.S. Pat. Nos. 4,443,559 and 4,250,052 disclose a variety of catalyst structures for this use.
Placing the particulate catalyst loose on standard distillation trays has also been proposed. See, for example, U.S. Pat. No. 4,215,011 and U.K. patents GB 2,096,603 and 2,096,604. The placement of the catalyst in the downcomers of standard distillation columns has been proposed as in U.S. Pat. 3,634,534. Fluidization of the catalyst on the trays has also been suggested as in U.S. Pat. No. 4,471,154. Some deficiencies of such fluidized beds were recognized in Chemiker Zeitung Chemische Apparatur, vol. 90, no. 13, July 1966 and U.S. Pat. No. 4,215,011. Quang, et al, in U.S. Pat. No. 4,847,430 and Nocca, et al in U.S. Pat. No. 4,847,431 disclose loading the particulate catalyst on alternating trays of a distillation column and with a gas by pass about the catalyst loaded trays.
So far, the most commercially successful arrangement has been to the place the particulate catalyst in closed pockets disposed along a fiber glass cloth belt.
The main problems sought to be overcome by the improvements have been the reduction of pressure drop through the column and provision of sufficient contact of the reactants with the catalyst while providing for good vapor liquid contact for the fractional distillation. Many useful catalysts are in the form of fine particulate powders which preclude their use directly as distillation components. Even larger extruded pellets do not lend themselves well as distillation structures. Hence the use of cloth belts, cages and support trays. While larger catalysts structures have been proposed, the porosity requirements of many catalytic materials limit their structural integrity. Many catalysts which rely on outer surface activity only and which might have the strength for larger structures are useful only for gas phase reactions, such as maleic anhydride production.